upright=1.5, Illustrated diagram of a closed-cycle gas-core nuclear-thermal rocket ("nuclear lightbulb"). A nuclear lightbulb is a hypothetical type of spacecraft engine using a

gaseous fission reactor A gas core reactor, and the very closely related vapor core reactor, is a proposed kind of nuclear reactor in which the nuclear fuel would be in a gaseous state rather than liquid or solid. In this type of reactor, the only temperature-limiting mat ...

to achieve

nuclear propulsion Nuclear propulsion includes a wide variety of propulsion methods that use some form of nuclear reaction as their primary power source. Many aircraft carriers and submarines currently use uranium fueled nuclear reactors that can provide propulsio ...

. Specifically, it would be a type of

gas core reactor rocket Gas core reactor rockets are a conceptual type of rocket that is propelled by the exhausted coolant of a gaseous fission reactor. The nuclear fission reactor core may be either a gas or plasma. They may be capable of creating specific impulses ...

that uses a

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

wall to separate the

nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other atomic nucleus, nuclear devices to generate energy. Oxide fuel For fission reactors, the fuel (typically based on uranium) is ...

from the

coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corr ...

and

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...

. It would be operated at temperatures of up to 22,000°C where the vast majority of the

electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...

emissions are in the hard

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

range. Fused silica is almost completely transparent to this light, so it would be used to contain the

uranium hexafluoride Uranium hexafluoride, sometimes called hex, is the inorganic compound with the formula . Uranium hexafluoride is a volatile, white solid that is used in enriching uranium for nuclear reactors and nuclear weapons. Preparation Uranium dioxide is co ...

and allow the light to heat

reaction mass Working mass, also referred to as reaction mass, is a mass against which a system operates in order to produce acceleration. In the case of a chemical rocket, for example, the reaction mass is the Product (chemistry), product of the burned fuel sh ...

in a rocket or to generate electricity using a

heat engine A heat engine is a system that transfers thermal energy to do mechanical or electrical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, pa ...

photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commerciall ...

Rocket engine

Like all nuclear rocket designs, the nuclear lightbulb can greatly exceed the exhaust speed and

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...

of a chemical rocket. However, it also does not involve the release of any radioactive material from the rocket, unlike

open cycle Open is a manufacturer of performance gravel bike and road bike frames based in Basel. Founded by Andy Kessler (cycling), Andy Kessler and Gerard Vroomen in 2012, the company debuted with a single model, the O-1.0. It was claimed to be the lightes ...

designs which would cause

nuclear fallout Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...

if used in a planetary atmosphere (e.g. Project Orion). The theoretical

(''I''_sp) range from 1500 to 3000 seconds.

Electrical power generation

As a method to generate electricity, nuclear lightbulbs are extremely efficient because higher-temperature heat contains more

Gibbs free energy In thermodynamics, the Gibbs free energy (or Gibbs energy as the recommended name; symbol is a thermodynamic potential that can be used to calculate the maximum amount of Work (thermodynamics), work, other than Work (thermodynamics)#Pressure–v ...

than the low-temperature heat produced in current fossil-fuel plants and water-cooled nuclear reactors.

References

*. * * Nuclear reactors Nuclear spacecraft propulsion Nuclear technology {{nuclear-tech-stub